Process of inhibiting corrosion



United States Patent 3,014,864 PROCESS OF INHIBITING CORROSION William B. Hughes and Verner L. Stromberg, Webster Groves, Mo., assignors to Petrolite Corporation, Wilmington, Del., a corporation of Delaware No Drawing. Original application Mar. 3, 1958, Ser. No. 718,401, now Patent No. 2,987,514, dated June 6, 1961. Divided and this application Dec. 28, 1959, Ser.

11 Claims. (Cl. 252-855) POLYESTERS This application is a division of application Serial No. 718,401, filed March 3, 1958, now U.S. Patent No. 2,987,514.

This invention relates to polyesters of hydroxyaliphatic cyclic amidine compounds and polycarboxylic acids (hereafter referred to as polyesters) More particularly, invention relates to a process of preparing these polyesters which comprises reacting a hydroxyaliphatic cyclic amidine, for example, a hydroxyaliphatic imidazoline or tetrahydropyrimidine with at least a stoichiometrical amount of a polycarboxylic acid. This invention also relates to a process of using these polyesters as corrosive inhibitors in preventing the corrosion ofmetals, most particularly iron, steel and ferrous alloys.

Heretofore, a wide variety of cyclic amidine compounds have been employed to inhibit the corrosion of oil well equipment. Although we had expected that hydroxyaliphatic cyclic amidines would also be effective in inhibiting oil field corrosion, we found that these com pounds had very poor corrosion inhibiting properties.

However, we have now unexpectedly discovered that the derivatives of these hydroxyaliphatic cyclic amidines, particularly polyester derivatives thereof, are very effective corrosion inhibitors, in many cases or more times as effective as the corresponding hydroxyaliphatic cyclic amidine.

The corrosion inhibitors disclosed herein are particularly useful in preventing the corrosion of oil equipment, for example, in producing wells, pipe lines, refineries, tank storage, etc., which are in contact with corrosive oilcontaining medium, for example, in oil wells producing corrosive oil or oil-brine mixtures in refineries, and the like. These compositions possess properties which impart to metals resistance to attack by a wide variety of corrosive agents, among which may be mentioned brines, organic and inorganic acids, CO H 0, 0 etc., and combinations thereof.

More specifically, the above described compounds may be described by the formulae:

A (The dotted lines indicate the undetermined structure probably polymeric.)

I 3,014,864 Patented Dec. 26, 1961- l (3) 111 o N \NR A in in which Bil and n is a whole number 1 or greater, for example, 1-3, but preferably 2, and R is the polyester group formed by the reaction of a hydroxy-containing alkylene, polyoxyalkylene, etc., group with the polycarboxylic acid.

More specifically, the corrosion inhibiting aspect of this invention relates to a method for inhibiting corrosion of ferrous metals .by hydrocarbon fluids containing Water and corrosive materials, such as H S, CO inorganic acids, organic acids, etc., combinations of these materials with each other, combinations of each of said corrosive materials with oxygen, and combinatioins of said materials with each other and oxygen, which comprises adding to said fluids at least 5 parts per million of the above polyesters, said compounds being sufiiciently soluble in the hydrocarbon fluid to inhibit corrosion.

HYDROXY ALIPHATTC CYCLE AMIDINE The expression cyclic amidines is employed in its usual sense to indicate ring compounds in which there are present either 5 or 6 members, and having 2 nitrogen atoms separated by a single carbon atom supplemented by either two additional carbon atoms or three additional carbon atoms completing the ring. All the carbon atoms may be substituted. In the present instance, the nitrogen atom of the ring, involving two monovalent linkages (the 1position) is substituted with an hydroxy aliphatic group.

These cyclic amidines are further characterized as being substituted imidazolines and tetrahydropyrimidines in which the two-position carbon of the ring is generally bonded to a hydrocarbon radical or comparable radical derived from an acid, such as a low molal fatty acid, a high molal fatty acid or comparable acids, polycarboxy acids and the like.

For details of the preparation of imidazo-lines substituted in the 2-position from amines, see the following U.S. patents, U.S. No. 1,999,989, dated April 30, 1935, Max Bochmuhl et al.; U.S. No. 2,155,877, dated April 25, 1939, Edmund Waldmann et al.; and U.S. No. 2,155,- 878, dated April 25, 1939, Edmund Waldmann et a1. Also see Chem. Rev. 32, 47' (43), and Chem. Rev. 54, 593 (54).

Equally suitable for use in preparing compounds of our invention and for the preparation of tetrahydropyrimidines substituted in the 2-position are the polyamines containing at least one primary amino group and at least one secondary amino group, or another primary amino group separated from the first primary amino group by three carbon atoms instead of being separated by only 2 carbons as with imidazolines. This reaction, as in the case of the imidazolines, is generally carried out by heating the reactants to a temperature at which 2 moles of water are evolved and ring closure is efiected. For details of the preparation of tetrahydropyrimidines, see German Patent No. 700,371, dated December 18, 1940, to Edmund Waldmann and August Chwala; German Patent No. 701,322, dated January 14, 1941, to Karl Kiescher, Ernst Urech and Willi Klarer, and U.S. Patent No. 2,194,419, dated March 19, 1940, to August Chwala.

Substituted imidazolines and tetrahydropyrimidines are obtained from a variety of acids beginning with the one-carbon acid (formic) through and including higher fatty acids or the equivalent having l-30 carbon atoms, for example, 8-22 carbon atoms. Modified fatty acids also can be employed as, for example, phenyl stearic acid or the like. Cyclic acids may be employed, including naphthenic acids. A variety of other acids including benzoic acid, substituted benzoic acid, salicylic acid, and the like, have been employed to furnish the residue RC from the acid RCOOH in which the C of the residue RC-- is part of the ring. The fatty acids employed, for example, may be saturated or unsaturated. They may be hydroxylated or nonhydroxylated. Branched long chain fatty acids may be employed. See J. Am. Chem. Soc. 74, 2523 (1952). This applies also to the lower molecular weight acids as well.

Among sources of such acids may be mentioned pie, ricinstearolic acid, the hydroxyeicosanoic acids, for example, hydroxyarachidic acid, the hydroxydocosanoic acids, for example, hydroxybehenic acid, and the like.

Examples of acetylated hydroxy acids comprise ricinoleyl lactic acid, acetyl ricinoleic acid, chloroacetyl ricinoleic acid,'and the like.

Examples of the cyclic aliphatic carboxylic acids comprise those found in petroleum called naphthenic acids,

hydnocapric and chaulmoogric acids, cyclopentane carboxylic acids, cyclohexanecarboxylic acid, campholic acid, fencholic acids, and the like.

Examples of aromatic monocarboxylic acids comprise benzoic acid, substituted benzoic acids, for example, the

' drogenated animal and vegetable oils are advantageously employed. Fatty and similar acids include those derived from various waxes, such as beeswax, spermaceti, montan wax, Japan wax, coccerin and carnauba wax. Such acids include carnaubic acid, cerotic acid, lacceric acid,

straight chain and branched chain, saturated and unsaturated, aliphatic, cycloaliphatic, aromatic, hydroaro matic, aralkyl acids, etc.

Examples of saturated aliphatic monocarboxylic acids comprises: acetic, propionic, butyric, valeric, caproic, he'ptanoic, caprylic, nonanoic, capric, undecanoic, lauric,

tridecanoic, myriatic, pentadecanoic, palmitic, heptadec-,

anoic, stearic, nonadecanoic, eicosanoic, heneicosanoic, docosanoic, tricosanoic, tetracosanoic, pentacosanoic, cerotic, heptacosanoic, montanic, nonacosanoic, melissic and the like.

Examples of ethylenic unsaturated aliphatic acids comprise: acrylic, methacrylic, crotonic, anglic, teglic, the pentenoic acids, the hexenoic acids, for example, hydrosorbic acid, the heptenoic acids, the ocetenoic acids, the nonenoic acids, the decenoic acids, for example, lauroleic, linderic, etc., the tridecenoic acids, the tetradecenoic acids, for example, rnyristoleic acid, the pentadecenoic acids, the hexadecenoic acids, for example, palmitoleic acid, the heptadecenoic acids, the octodecenoic acids, for

montanic acid, psyllastearic acid, etc. One may also employ higher molecular weight carboxylic acids derived by oxidation and other methods, such as from paraflin wax, petroleum and similar hydrocarbons; resinic and hydroaromatic acids, such as hexahydrobenzoic acid, hydrogenated naphthoic, hydrogenated carboxy diphenyl, naphthenic, and abietic acid; aralkyl and aromatic acids, such as Twitchell fatty acids, naphthoic acid, carboxydiphenyl pyridine carboxylic acid, blown oils, blown oil fatty acids and the like.

example, petrosilenic acid, oleic acid, elaidic acid, the

nonadecenoic acids, for example, the eicosenoic acids, the decosenoic acids, for example, erucici acid, brassidic acid, cctoleic acid, the tetracosenic acids, and the like.

Examples of dienoic acids comprise the pentadienoic acids, the hexadienoic acids, for example, sorbic acid, the octadienoic acids, for example, linoleic, and the like. Examples of the trienoic acids comprise the octadecatrienoic acids, for example, linoleic acid, eleostearic acid, pseudo-ele'ostearic acid, and the like.

'Carboxylic acids containing functional groups such as hydroxy groups can be employed. Hydroxy acids, particularly the alpha hydroxy acids, comprise glycolic acid, lactic acid, the hydroxy-Valerie acids, the hydroxy caproic acids, the hydroxyheptanoic acids, the hydroxy caprylic acids, the hydroxynonanoic acids, the hydroxycapric acids, the hydroxydecanoic acids, the hydroxy lauric acids, the'hydroxy tridecanoic acids, the hydroxymyristic acids, the hydroxypentadecanoic acids, the hydroxypalmitic acids, the hydroxyhexadecanoic acids, the hydroxyheptadecanoic acids, the hydroxy stearic acids, the hydroxyoctadecenoic acids, for example ricinoleic acid, ricinelaidic acid, hydroxyoctadecynoic acids, for exam- Other suitable acids include phenylstearic acid, benzoylnonylic acid, cetyloxybutyric acid, cetyloxyacetic acid, chlorstearic acid, etc.

Examples of the polycarboxylic acids compirse those of the aliphatic series, for example, oxalic, malonic, succinic, glutaric, ad-ipic, pimelic, suberic, azelaic, sebacic, nonanedicarboxylic acid, decanedicarboxylic acids, undecanedicarboxylic acids, and the like.

Examples of unsaturated aliphatic polycarboxylic acids comprise fumaric, maleic, mesocenic, citraconic, glutonic, itaconic, muconic, acenitic acids, and the like.

Examples of aromatic polycarboxylic acids comprise phthalic, isophthalic acids, terephthalic acids, substituted derivatives thereof (e.g. alkyl, chloro, alkoxy, etc. derivatives), biphenyldicarboxylic acid, diphenylether dicarboxylic acids, diphenylsulfone dicarboxylic acids and the like.

Higher aromatic polycarboxylic acids containing more than two carboxylic groups comprise hemimellitic, trimellitic trimesic, mellophanic, prehnitic, pyromellitic,

' mellitic acid and the like.

Other polycarboxylic acids comprise the dimeric, trimeric and polymeric acids, for example, diricinoleic acid, tr'iricinoleic acid, polyricinolcic acid, and the like. Other polycarboxylic acids comprise those containing ether groups, for example, diglycolic acid. Mixtures of the above acids can be advantageously employed.

In addition, acid precursors such as esters, acid chlorides, glyceridcs, etc. can be employed in place of the free acid. 7

When the acid used in preparing the cyclic amidine has functional groups, such as hydroxy groups, this should be taken into consideration in calculating the stoichiometry of the subsequent esterification with the polycarboxylic acids.

Hydroxy substituted imidazolines and tetrahydropyrimidines can beobtained in the manner described above from a wide variety of polyamines containing hydroxy groups. Thus, where one starts with a polyamine, for example, a diamine of the following formula H NHgR- N-lV-OH or NH Rl I(OR)nOH where R has for example a 2 or 3 carbon main chain, one obtains the compounds of this invention. In addition, one can start with ethylene diamine or with 1, 2-propylene diarnine, 1, 3-propylenediamine or other polyamines and then react the cyclic amidine so obtained with alkylene oxides so as to produce a terminal hydroxy group since the nitrogen bonded hydro-gen on the l-position on the ring reacts with alkylene oxides. In addition, the hydroxyalkylene groups attached to the cyclic amidine ring can be oxyalkylated.

Alkylene oxides comprise those of the general formula,

RCHr-CH2 where R is an alkyl group. Among the alkylene oxides that may 'be employed are ethylene, propylene, butylene, octylene, etc. oxides, etc. Other oxyalkylation agents such as glycide, epichlorohydrine, etc. can be employed.

Thus, compounds within the scope of this invention which may react with polycarboxylic acids comprise compounds of the formulae:

is the residue derived from the carboxylic acid, where R is a hydrocarbon radical having, for example, up to about 30 carbon atoms, and hydrocarbons in which the carbon atom chain is interrupted by oxygen, etc.; n is 2 or 3; and B is a hydrogen or a hydrocarbon radical, for example, an alkyl radical; and D is a hydroxy-containing radical, for example ROH or R(OR) OH, wherein n is a whole number, for example, 1-10 or higher, but preferably 1-5, and (CB is, for example, a divalent radical of the formula:

CHg-CH, oHi-OHr-OHi-, -([JHCH3 CH3 CH-CH, CHg-CHrCHz etc.

H: CH: CH:

In general, the hydroxy alkyl cyclic amidines are prepared by reacting a polyamine containing a terminal alkanol group with a carboxylic acid at temperatures of from 150-175 C. employing as azeotroping agent such as xylene to remove water. The reaction time of 3-4 hours is employed. Completion of reaction is judged by the separation of 2 moles of H 0 for each carboxylic acid group.

. Since the preparation of cyclic amidines is so well known (see above cited patents), it is not believed that any examples are necessary to illustrate such a wellknown procedure. However, for purposes of illustration, the following are included:

Example a I A solution of 1 mole of hydroxyethyl ethylene diamine, noornonigomonmni and 1 mole of oleic acid in 300 grams of xylene are charged to a flask and brought to reflux, the mixture being heated under a Dean-Stark water trap-condenser in order to distill otf the water-xylene azeotrope mixture, separate the water and to return xylene to the reaction mixture. Reflux is continued at a temperature of C. for about 3 /2 hours until about 2 moles of Water are removed. The product is 317E213 Example 9b The above example is repeated except that hydroxy ethyl propylene diamine 1-3,

is employed in place of hydroxyethylethylene diamine and stearic acid is employed in place of leic acid. The product produced is /Cg2 (3E1 ([311: N NOH2CH2OH l Civ ss Example 4c Example 10a is repeated with the same amine HO CH2CH2CH2CH2NH2 (2 moles) except that a polycarboxylic acid, sebacic acid (1 mole) is employed. Instead of two moles of water being removed, as in the prior example, 4 moles of water are removed. The product is CHr-CH: (FHz-CH HO-CHr-CHs-N N N NCH2CH2OH C-(CHg)s-C Example 20d Example 41: is repeated with nocmomgomomonmm (2 moles) and a different polycarboxylic acid, terephthalic acid (1 mole). As in the prior example, 4 moles of water are removed. The product is /CH: /Ggz $312 (13E: (1111: $111 HO CHn-CHr-N N N N-CHrOHzOH Jr/Ha: (50% solution in xylene) is reacted with 1 mole of ethylene oxide at a temperature of 125130 C. and a pressure of 10-15 p.s.i. The time regulator is set to add ethylene oxide over hour followed by additional stirring for another /2 hour to insure complete reaction.

9 THE POLYCARBOXYLIC ACIDS The polycarboxylic acid employed to react with the hydroxy cyclic amidine can be varied widely. In general, they can be expressed as:

where R comprises a saturated or unsaturated aliphatic radical, a cycloaliphatic radical, an aromatic radical, and the like; and X is a whole number equal to 2 or more, for example, 2-4, but preferably 2.

Examples of the polycarboxylic acids comprise those of the aliphatic series, forexample, oxalic, malonic, succinic, glutaric, adipic, pimelic, suberic, azelaic, sebacic, nonanedicarboxylic acid, decanedicarboxylic acids, undecanedicarboxylic acids, and the like.

Examples of unsaturated aliphatic polycarboxylic acids comprise fumeric, maleic, mesocenic, citraconic, glutonic, itaconic, muconic, aconitic acids, and the like.

Examples of aromatic polycarboxylic acids comprise phthalic, isophthalic acids, terephthalic acids, substituted derivatives thereof (e.g. alkyl, chloro, alk-oxy, etc. derivatives), biphenyldicarboxylic acid, diphenylether dicarboxylic acids, diphenylsulfone dicarboxylic acids and the like.

Higher aromatic polycarboxylic acids containing more than two carboxylic groups comprise hemimellitic, trimellitic, trimesic, mellophanic, prehnitic, pyromellitic acids, mellitic acid, and the like.

Other polycarboxylic acids comprise the dimeric, trimeric and polymeric acids, for example, dilinoleic acid, trilinoleic acid, polylinoleic acid, and the like, for example, those sold by Emery Industries. Other polycarboxylic acids comprise those containing ether groups, for example, diglycolic acid. Mixtures of the above acids can be advantageously employed.

In addition, acid precursors such as esters, acid chlorides, glycerides, anhydrides, etc. can be employed in place of the free acid.

THE POLYESTERS The products of this invention are polyesters of cyclic amidines. They may be expressed by the following general formula:

i )n wherein R comprises the radical of the polycarboxylic acid and 0 II -o o@ represents the cyclic amidine groups esterified with each carboxylic acid group of the polycarboxylic acid. Thus, the products of the invention comprise:

A o N N-xii n when X comprises (R"O) for example n=1- 5 and R is'the radical derived from the polycarboxylic acid.

'hen the bicyclic amidines' are employed as hydroxy precursors, the following type of compounds, which is polymeric in nature, is formed:

Example 1012A Two moles of the product of Example 10a and one mole of adipic acid are dissolved in 300 grams of toluene and the reaction mixture, heated to reflux, is azeotroped using a DeanStark trap in the manner of 10a until 2 moles of water are removed. The temperature is maintained at ISO- over about 3.5 hours. The product is Example Ma]? The process of the prior example is repeated except that sebacic acid is employed. The product is Example IOaC The process of the prior example is repeated except that terephthalic acid is employed. The product is I uHss ii zs Example 10aD The process of the prior example is repeated except that a tricarboxylic acid was employed in ratios of 3 moles of to each mole of a trimeric acid, trilinoleic acid. The

product former is a polyester of the formula I CHHBI 3 where R is the residue of the tn'meric acid.

1 1 Example 917C The process of the prior example is repeated except that 1 N-orncrnon 31113 is reacted with diglycolic acid in ratios of 2 moles to 1 to yield Example 20.4

The process of the prior example is repeated except that one mole of and one mole of terephthalic acid was employed to yield a composition of the formula Example zen The process of Example 2cA is repeated except that succinic anhydride is employed in place of terephthalic acid. The anhydride is added to the hydroxyaliphatic amidinc over of an hour at 50-60 C. employing two moles of anhydride for each mole of amidine. "Ihis product is then reacted in a second stage with a second mole of the amidine by esterifying in the presence of an azeotropic agent at 150-475 C. to yield,

I Pt

The above methods are typical methods of preparation. The following polyesters are prepared by these methods. Each ester will have the same basic number shown in the prior tables, for example, 1a, a, etc., to indicate thehlydroxy cyclic amidine employed. In addition, it willibear a capital letter A, B, C, D, etc., which indicates that it has been acylated, for example, MA, MB, lOaC, etc. In each example, the carboxylic acid groups on the acid were equivalent to the moles of hydroxygroups on the cyclic amidines.

Mole ratio amidine/ acid Example Acid l 2 stage process.

USE AS CORROSION INHIBITOR More specifically, this phase of the invention relates to the inhibition of corrosion in the petroleum industry with specific reference to producing wells, pipe lines, refineries, tank storage, etc.

The use of a corrosion inhibiting agent in the oil industry and other industries, and particularly for the protection of ferrous metals, is well known. For example, see US. Patents Nos. 2,736,658, dated February 28, 1954, to Pfohl et al., and 2,756,211, dated July 24, 1956, to Jones, and 2,727,003, dated December 13, 1955, to Hughes.

More specifically then, and particularly from the standpoint of oil production, this aspect of the invention relates to inhibiting corrosion caused by hydrogen sulfide, carbon dioxide, inorganic acids, organic acids, combinations of each with oxygen, and with each other and oxygen. More particularly, it relates to treating wells to mitigate metal corrosion and associated diificulties.

It should also be pointed out that the corrosiveness of oil well brines will vary from well to well, and the proportion of corrosion inhibiting agent added to the well fluids should also be varied from well to well. Thus, in some wells it may be possible to effectively control corrosion by the addition of as little as 5 p.p.m. of our new compositions to the well fluids, whereas in other wells, it may be necessary to add 200 p.p.m. or more.

In using our improved compositions for protecting-oil well tubing, casing and other equipment which comes in contact with the corrosive oil-brine production, we find that excellent results may be obtained by injecting anappropriate quantity of a selected composition into a producing well so that it may mingle with the oilbrine mixture and come into contact with the casing, tubing, pumps and other producing equipment. We, for example, can introduce the inhibiting composition into the top of the casing, thus causing it to flow down into the well and thence back through the tubing, etc. In general, we have found that this procedure sulfices to inhibit corrosion throughout the entire system of production, and collection, even including field tankage.

In case serious emulsion or gel problems are encountered, demulsifiers are advantageously added. This is important not only to avoid the troublesome emulsions and gels themselves, but also to improve corrosion inhibition. The explanation of less effective corrosion inhibition in the presence of emulsions apparently is that the inhibitor is somewhat surface-active. That is, it is concentrated at interfacial surfaces. Since this surface is great in an emulsion, most of the inhibitor will be concentrated in these interfaces and little will remain in the body of the oil for deposition on the metal surfaces. In many 'wells, oil-in-water type emulsions often occur naturally. In such wells the inhibitors herein described tending to form water-in-oil type emulsions, often decrease the emulsion problems naturally present. Thus, in addition to being effective corrosion inhibitors, the herein described products tend to eliminate emulsion problems which sometimes appear when some of the present day inhibitors are used in oil Wells or refinery processing.

The method of carrying out our process is relatively simple in principle. The corrosion preventive reagent is dissolved in the liquid corrosive medium in small amounts and is thus kept in contact with the metal surface to be protected. Alternatively, the corrosion inhibitor may be applied first to the metal surface, either as is, or as a solution in some carrier liquid or paste. Continuous application, as in the corrosive solution, is the preferred method, however.

The present process finds particular utility in the protection of metal equipment of oil and gas wells, especially those containing or producing an acidic constituent such as H 8, CO inorganic, organic acids, and the like. For the protection of such Wells, the reagent, either undiluted or dissolved in a suitable solvent, is fed down the annulus of the Well between the casing and producing tubing where it becomes commingled with the fluid in the Well and is pumped or flowed from the Well with these fluids, thus contacting the inner Wall of the casing, the outer and inner wall of tubing, and the inner surface of all well-head fittings, connections and flow lines handling the corrosive fluid.

Where the inhibitor composition is a liquid, it is conventionally fed into the well annulus by means of a motor driven chemical injector pump, or it may be dumped periodically (e.g., once every day or two) into the annulus by means of a so-called boll weevil device or similar arrangement. Where the inhibitor is a solid, it is dropped into the Well as a solid lump or stick, blown in as a powder with gas, or it may be washed in with a small stream of the well fluid or other liquids. Where there is gas pressure on the casing, it is necessary, of course, to employ any of these treating methods through a pressure equalizing chamber equipped to allow introduction of reagent into the chamber, equalization of pres sure betwen chamber and casing, and travel of reagent from chamber to well casing.

Occasionally, oil and gas wells are completed in such a manner that there is no opening betwen the annulus and the bottom of the tubing or pump. This results, for example, when the tubing is surrounded at some point by a packing held by the casing or earth formation below the casing. In such wells the reagent'may be introduced into the tubing through a pressure equalizing vessel, after stopping the flow of fluids. After being so treated, the well should be left closed in for a period of time suflicient to permit the reagent to drop to the bottom of the well.

' For injection into the well annulus, the corrosion inhibitor is usually employed as a solution in a suitable solvent, such as mineral oil, methylethyl ketone, xylene, kerosene, or even water.

For treating Wells with packed-off tubing, the use of solid sticks or plugs of inhibitor is especially convenient. These may be prepared by blending the inhibitor With a mineral wax, asphalt or resin in a proportion sufficient to give a moderately hard and high-melting solid which can be handled and fed into the well conveniently.

The amount of corrosion preventive agent required in our process varies with the corrosiveness of the system, but where a continuous or semi-continuous treating procedure is carried out as described above, the addition of reagent in the proportion of from 5 parts per million to 1000 parts per million or more parts of corrosive fluid will generally provide protection.

These corrosion inhibitors can be used in combination with other well-known corrosion inhibitors, for example, the cyclic amidine structures, the amide cyclic amidine structures, and the amino cyclic amidine structures, as disclosed in the Blair and Gross Reissue Patent No. 23,227. When the herein described products are mixed with corrosion inhibitors of the conventional type in the ratio of one-to-three, one-to-one, three-to-one, or the like, in numerous instances the effectiveness of the corrosion inhibitor thus obtained is often significantly greater than the use of either one alone.

Since these products are basic they can be combined with various acids to produce salts in which oil solubility is increased or decreased. Likewise, water solubility is increased or decreased. For instance, the products may be mixed with one or more moles of an acid, such as higher fatty acids, dimerized fatty acids, naphthenic acids, acids obtained by the oxidation of hydrocarbons, as well as sulfonic acids such as dodecylbenzene sulfonic acid, petroleum mahogany acids, petroleum green acids, etc.

What has been said in regard to the acids which increase oil solubility and decrease water solubility applies with equal force and effect to acids of the type, such as acetic acid, hydroxyacetic acid, gluconic acid, etc., all of which obviously introduce hydrophile character when they form salts or complexes. if complexes are formed. For example, any of the acids described above in preparing the cyclic amidine are useful in preparing their salts.

As pointed out previously, the addition of corrosion inhibitors, particularly in the form of a solution by means of a metering pump or the like, is common practice. The particular corrosion inhibitors herein described are applied in the same manner as other corrosion inhibitors intended for use for the same purpose. For sake of brevity, one may use the corrosion inhibitor in solution form by dissolving it in a suitable solvent, such as mineral oil, methyl ethyl ketone, xylene, kerosene, high boiling aromatic solvent, or even water.

The following examples are presented to illustrate the superiority of the instant compounds as corrosion inhibitors:

Hot stirring tests (140 F.).-These tests are run on synthetic fluids. The procedure involves the comparison of the amount of iron in solution after a predetermined interval of time of contact of a standardized iron surface with a two-phase corrosive medium with similar determinations in systems containing inhibitors.

Six hundred ml. beakers equipped with stirrers and heaters are charged with 400 ml. of 10% sodium chloride containing 500 p.p.m. acetic acid and ml. of mineral spirits. The liquids are brought to temperature and a 1 x 1 inch sand blasted coupon is suspended by means of a glass hook approximately midway into the liquid phase of the beaker. The stirrer is adjusted to agitate the liquids at such a rate as to provide good mixing of the two layers.

After 30 minutes samples of the aqueous phase are taken and the iron content of each sample is determined by measuring the color formed by the addition of hydrochloric acid and potassium thiocyanate in a photoelectric colorimeter.

The protection aflorded by an inhibitor is measured by X 100 percent protection where A, is the present light absorbed by an uninhibited sample and A, is the same value for an inhibited sample.

Static weight loss tests-These tests have been run on both synthetic and naturally occurring fluids. The test procedure involved the measurement of the corrosive action of the fluids inhibited by the compositions herein described upon sandblasted S.A.E. 1020 steel coupons measuring 78 x 3% inches under conditions approximating those found in an actual producing well, and the comparison thereof with results obtained by subjecting identical test coupons to the corrosive action of identical fluids containing no inhibitor.

Clean pint bottles were charged with 200 ml. of 10% sodium chloride solution saturated with hydrogen sulfate and 200 ml. of mineral spirits and a predetermined amount of inhibitor was then added. In all cases the inhibitor concentration was based on the total volume of fluid. Weighed coupons were then added, the bottles tightly sealed and allowed to remain at room temperature for three days. The coupons were then removed, cleaned by immersion in inhibited 10% hydrochloric acid, dried and weighed.

The changes in the weight of the coupons during the corrosion test were taken as a measurement of the effectiveness of the inhibitor compositions. Protection percentage was calculated for each test coupon taken from the inhibited fluids in accordance with the following formula:

L X l=percent protection in which L is the loss in weight of the coupons taken TABLE VII Static weight loss testinhibitar concentration, 100 p.p.m.

R R Percent protection Dilinolcic 88. 9

Tcrephthalic 97. 1

Dilinoleim 92.0

Tcrephthah 90. 8

N\ o NCH2CHgOI-I we I C'rvHaa OTHER USES These products are effective not only as corrosion inhibitors but can be used for a number of other purposes. For instance, they are useful as asphalt additives to increase the adhesiveness of the asphalt to the mineral aggregates. In the form of water soluble salts, they are useful as bactericides in the secondary recovery of oil. The hydroxy cyclic amidines may be subjected to extensive oxyalkylation by means of ethylene oxide, propylene oxide, butylene oxide, or the like prior to re action with the polyacids. These are oxyalkylated and still have oil solubility as, for example, by the addition of propylene oxide or butylene oxide, or are oxyalkylated to produce water solubility as, for example, by means of ethylene oxide or glycide. They are also oxyalkylated by combinations of propylene oxide and ethylene oxide so that both water solubility and oil solubility remain. Thereupon they are reacted with polycarboxylic acids. Such products are useful for a variety of purposes and particularly for those where nonionic surfactants or sequestered cationic surfactants are indicated.

In addition, the compounds of this invention have the following applications:

Agriculture: additive for kerosene used in phenothiazine, pyrethrum sprays, fungicides, herbicidal oils.

Anti-static treatment: for hotel rugs, hospital floors, automobile upholstery, plastic and wax polishes, wool oils, lubricants for synthetic fibers.

Building materials: water repellent treatment for plaster, concrete, cement, roofing materials, air entrainment, floor sealers, linoleum.

Cosmetics: Formulation of anti-perspirants, deodorants. sun screens, hair preparations.

De-emulsifying: in antibiotic extraction, breaking crude oil and water-gas for emulsions.

Detergents: metal cleaning emulsions, lens cleaners, floor oils, dry cleaning detergents, radiator flushes, cesspool acid, boiler scale solvents, germicidal corrosion-inhibited acid, detergents for dairies, enamel equipment. toilet bowls.

Leather: Flat liquoring oils, pickling, acid degreasing, dye fixative.

Metals: rust preventive oils, cutting oils, water displacing compounds, pickling inhibitor, solvent degreasing.

Paints: for improved adhesion of primers, preventing water spotting in lacquers, anti-skinning, pigment flushing, grinding and dispersing, anti-feathering in inks.

Petroleum: Used as a germicide in flood water treatment, demulsifying fuel oil additives, anti-strip agent in asphalt emulsions and cutbacks. I

Textiles: in rubberizing, textile oils,'dyeing assistants, softening agents. I

Miscellaneous: bentonite-amine complexes, metalamine complexes, preparation of pentachlorphenates, quaternaries, plastisols, and rodent repellents.

Having thus described our invention what we claim as new and desire to obtain by Letters Patent, is:

l. A process of inhibiting the corrosion of ferrous metals in a hydrocarbon system which is characterized by contacting such metals with an ester of the formula where B is selected from the group consisting of hydrogen and a lower alkyl group, A is a lower alkylene group having at least two carbon atoms, R and R are residues derived from carboxylic acids, each having 1-36 carbon atoms and where R is R=when the acid from which it is derived is a dicarboxylic acid and where R is RE when the acid from which it is derived is a tricarboxylic acid.

2. A process of inhibiting the corrosion of ferrous metals in a hydrocarbon system which is characterized by contacting such metals with an ester of the formula where R and R are carboxylic acid residues, each having 1-36 carbon atoms.

3. A process of inhibiting the corrosion of ferrous metals in a hydrocarbon system Which is characterized by contacting such metals with an ester of the formula where R and R are residues derived from carboxylic acids, each having 1-36 carbon atoms.

4. A process of inhibiting the corrosion of ferrous metals in a hydrocarbon system which is characterized by contacting such metals with a. polyester of and a dicarboxylic acid, where R is a residue derived from a carboxylic acid having 1-36 carbon atoms.

6. A process of inhibiting the corrosion of ferrous 7 l8 metals in a hydrocarbon system which is characterized by contacting such metals with a polyester of and a dicar-boxylic acid where R is a residue derived from carboxylic acids having a 1-36 carbon atoms.

7. A process of inhibiting the corrosion of ferrous metals in hydrocarbon systems which comprises contacting such metals with 8. A process of inhibiting the corrosion of ferrous metals in hydrocarbon systems which comprises contacting such metals with l' 0 IRC/N-CH OHZW- :(CHm

( 317Hsa 2 9. A process of inhibiting the corrosion of ferrous metals in hydrocarbon systems which comprises contacting such metals with r l u N N-omorno-o 10. A process of inhibiting the corrosion of ferrous metals in hydrocarbon systems which comprises contacting such metals with I ll N N-omorno-o =R where R is the residue of dilinoleic acid.

11. A process of inhibiting the corrosion of ferrous metals in hydrocarbon systems which comprises contacting such metals with Where R is the residue of dilinoleic acid.

References Cited in the file of this patent UNITED STATES PATENTS 2,211,001 Chwala Aug. 13, 1940 2,369,818 -De Groote et al Feb. 20, 1945 2,468,163 Blair et al Apr. 26, 1949 2,713,582 Smith July 19, 1955 2,773,879 Sterlin Dec. 11, 1956 2,889,193 Denman et al June 2, 1959' 2,950,246 Hughes Aug. 23, 1960 

1. A PROCESS OF INHIBITING THE CORROSIOU OF FERROUS METALS IN A HYDROCARBON SYSTEM WHICH IS CHARACTERIZED BY CONTACTING SUCH METALS WITH AN ESTER OF THE FORMULA 